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Summer 2010

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

dog-day cicada; Tibicen pruinosa

June 22, 2010

Dog-day cicadas: Big bugs abuzz

Save for bees humming and mosquitoes whining, local insects are mostly silent until about the first day of summer, when the loudest of them all begins to sing.

Dog-day cicadas are crawling out of the ground as mature nymphs that climb up tree trunks, split open and emerge as long- winged, bug-eyed adults that will live for only a few weeks. Unlike the black-and- orange periodical cicadas, which emerge in overwhelming numbers every 13 or 17 years, the larger, greenish dog-day cicadas are with us every summer.

Males do the droning , which is generated by a pair of ribbed membranes at the base of the cicada's hollow abdomen. Muscles distort these tymbals to make pulses of sound that

resonate in the insect's abdomen. The vibrations from a single cicada can reach 100 decibels and be heard a quarter-mile away.

U.S. Navy scientists, intrigued by the cicada's piercing signal, recently analyzed the efficiency of the insect's sound propagation. "Application of the same principles has the potential to improve radiated sound levels for sonar applications," says a 2009 report.

Male cicadas would prefer to impress a female. If drawn to his call, she will signal her interest with a flip of her wings.

Females use their ovipositor organ to saw small gashes into tree twigs, where they lay eggs. Nymphs will hatch after about six

weeks, drop to the ground, burrow down to a tree root and suck its juices for two to five years before maturing.

Listen to the calls from a few of the species found in the Washington area:

Northern dusk-singing cicada (Tibicen auletes)

Morning cicada, or swamp cicada (Tibicen tibicen)

Scissor-grinder cicada (Tibicen pruinosa)

Sources: Entomology departments of the University of Michigan and the University of Florida; Journal of the Acoustical Society of America